The present invention relates to a LED array flash for cameras, especially to a LED flashlight applied to cameras and formed by a LED array with a plurality of distribution pattern LED and a controller.
Xenon flash lamps are commonly used as photographic strobe lights due to high intensity of light generated by high voltage discharged between electrodes. The main advantages of the Xenon lamp are that spectral profile is uniform in the field of visible light and that is good chromaticity level and color rendering. Moreover, the Xenon lamp has short start-up time, inert gas without danger of explosion. However, it also has a plurality of disadvantages such as low lighting efficiency, short life, high cost and large amount of heat resulted. While being applied, the Xenon lamp consumes a lot power so that the flashlight is unable to be used quite often and the photo-sensor is adjusted by complicated software so as to achieve proper picture brightness.
LED (Light-Emitting Diode) is a semiconductor diode that emits light by electric exciting. Electric energy is converted into light energy directly. When electric current is applied, conduction electrons meet hole carriers and releases energy in the form of light. According to various materials with different energy levels being used, the LED emits light with different wavelength. Since, LED has advantages of compact volume, short start-up time and low pollution so that is has been applied to various fields. In recent years, the high power LED has been applied to cameras and can be used for a longer enough time so that brightness of the camera photo-sensor can be adjusted. Refer to US2007/195176, US2003/216151, and JP10-039795, LED may be replaced conventional Xenon lamps in cameras or phone cameras. However, brightness of single LED may be still not enough so that a LED array formed by a plurality of LED is used, as shown in U.S. Pat. No. 7,136,672, US2003/218689, U.S. Pat. No. 7,236,697, and JP2006-173622 etc. Because brightness of LED is not as high as traditional Xenon lamps, arrangement of LED in the LED array for photographing is quite important otherwise brightness of light on the target is not uniform. Moreover, the conventional control way such as pulse control or timer, brightness of each LED may be different from one another. Besides power consumption, the preset distribution pattern is another problem. Refer to FIG. 1, a conventional LED flashlight is formed by at least one LED light source 23, a LED die 233 and a LED board 24. Light emitted from the LED die 23 on the LED board 23 is reflected by a reflector 28 with paraboloid and is projected onto an object. However, while photographing object, under the condition that the light intensity of the LED light source 23 is limited, it is an important issue to make light from the LED light source 23 gather efficiently to form a preset distribution pattern on the object. To achieve the practice application, efficient lighting and lighting control is accomplishing the foregoing expectations.